Effect Thickness and Temperature Annealing on Structural and Optical Proportion of CuInTe 2 Thin Film

Transcription

1 AASCIT Journal of Materials 2016; 2(1): 1-5 Published online February ( Effect Thickness and Temperature Annealing on Structural and Optical Proportion of CuInTe 2 Thin Film Falah I. Mustafa 1, Bushrh K. Almaiyaly 2, Shamaa Qasim 2 Keywords CIT, Thin Film, Solar Cell, Semiconductors Received: January 2, 2016 Revised: January 13, 2016 Accepted: January 15, Solar Energy Research Center, Renewable Energy Directorate, Ministry of Higher Education and Scientific Research, Baghdad, Iraq 2 Physics Department, College of Education for pure Science, Ibn Alhaitham College, Baghdad University, Baghdad, Iraq address falah_im@yahoo.com (F. I. Mustafa), dr.bushra2009@yahoo.com (B. Almaiyaly), shama.kasem@yahoo.com (S. Qasem) Citation Falah I. Mustafa, Bushrh K. Almaiyaly, Shamaa Qasim. Effect Thickness and Temperature Annealing on Structural and Optical Proportion of CuInTe 2 Thin Film. AASCIT Journal of Materials. Vol. 2, No. 1, 2016, pp Abstract Thin films of CuInTe 2 (CIT) were deposited at room temperature on glass substrate with thickness 300 nm and 600 nm under vacuum pressure 10-5 torr by using physical thermally evaporation technique. The amorphous nature of as deposited thin films has been checked by XRD technique and after annealing temperatures (200, 400) C. It was found that the material has a polycrystalline structure preferentially oriented in the (112), (220)/(204) and (312)/(116) plains, which correspond to a tetragonal structure. The grain size of CIT increased with increasing the annealing temperature. The transmittances of the thin films are measured in the wavelength range nm by UV-VIS-IR spectrophotometer and optical absorption obeyed the direct transition process. The optical energy gab value increases with increasing annealing temperature as well as thickness. 1. Introduction CuInTe 2 (CIT) is a ternary chalcopyrite compound of the I-III-VI 2 family has been extensively studied due to their application in photovoltaic cell [1-3]. CIT material has direct band gap, a stronger quantum confinement effect and a larger Bohr radius more than of CuInGaSe 2 (CIGS), CuInSe 2 and CuInS 2 materials. The optical energy gap of CuInTe 2 thin films have range from 0.96 ev to 1.04 ev with absorption coefficient α cm -1 and can be prepared as both of p and n type absorbed materials that is suitable promising for energy conversion for solar cell application [4, 5]. The ternary compounds have a wide range of device application for economical and investigation of the structural and physical properties of thin film of these materials have been reported [6]. The highest reported power conversion efficiency with CIT absorber layer with efficiency 5.1% by using conventional Molecular beam Epitaxial (MBE) system [7]. Like CIGS, the CuInTe 2 which material one of the component absorber materials for solar cell application [8]. Recently, researchers have been consistently trying to understand a defect structural of this material since a new form of control over fundamental properties of ternary [9]. The purpose of the present work was to determine the optical constant and to study structural property variations of CIT thin films produced by the effects thickness and annealing treatment on both optical and structural properties of CIT thin films. The study result showed that the thin films as-deposited of

2 2 Falah I. Mustafa et al.: Effect Thickness and Temperature Annealing on Structural and Optical Proportion of CuInTe 2 Thin Film CIT are amorphous in structure while after annealing temperatures are polycrystalline. And the grain size of the particles increases as results of increasing the annealing temperature. It can be also concluded that CIT is a direct gap semiconductor, whose Eg value increasing with increasing annealing temperature as well as thickness. 2. Experimental Procedure The CIT material powder have prepared by using constituent element of 5N purity material of copper, indium and tellurium weighted in stoichiometric ratio, then sealed in a evacuated ampoule Quartz tube and put in the horizontal furnace and sometimes shacked the tube to ensure that the alloy mixing of the element and the mixture was heated at 1200 C for 12h and then drop the heated ampoule quickly with less than one second time from hot zone on to cold water container by quenching procedure. Thin films prepared by deposited material on glass substrate with using thermally heated of molybdenum boat by thermal evaporation technique under vacuum pressure ~ 10-5 mbar. The clean glass substrates kept at room temperature (RT) with thin films two thicknesses (300, 600) nm at the annealing temperatures (RT, 200, 400) C. The structural properties of the CIT films were investigated by using X-ray diffraction patterns which were recorded using Cukα radiation source and we have used Shimadzu spectrophotometer type, UV-VIS-IR ( ) nm spectrum to measure the optical transmission. Fig. 2. XRD patterns of the as-deposited CIT thin film at room temperatures with thickness at a: 300 nm and b: 600 nm. 3. Result and Discussion According to XRD test that is known the CIT powder sample represent chalcopyrite structure as shown in the figure1. The characteristic peaks of the chalcopyrite at miller indexes (112), (204), (116) were lying at approximate angles 2θ=24.8, 41.1 and 48.6 respectively, the peak heights and positions are in good agreement with data reported for the bulk material [10]. The thin films X-ray data were prepared by thermal evaporation technique on glass substrates with thickness (300, 600) nm at room temperature observed that as-deposited were amorphous structure as shown in the figure 2 (a, b). While the films were annealed at temperature (200, 400) C were polycrystalline diffraction patterns as shown in the figure 3. The peak intensity increased with increasing annealing temperature and the width of the peak decreased. Fig. 1. X-ray diffraction pattern of CIT powder sample.

3 AASCIT Journal of Materials 2016; 2(1): The crystallite size was estimate from the following Scherer equation (1): D= 0.9 λ / (2θ) cosθ (1) Fig. 3. XRD pattern of annealing CIT thin film at (200, 400) C with thickness (300, 600) nm. Where D is the crystallite size of the CIT material and sample λ is the X-ray wavelength (1.54 A), the samples θ (rad) and (2θ) (rad) are the Bragg diffraction angle and the full width at half maximum respectively, and all data were listed in tables (1, 2, 3). The results showed the same values of crystallite size increases with annealing temperatures for both thickness 300 nm and 600 nm. Table 1. The calculated values of inter-planar distance (d-values), with lattice parameter, crystallite size for the CIT powder. R. T / / Table 2. The calculated values of inter-planar distance (d-values), with lattice parameter, crystallite for the prepared CIT thin film at (200, 400) C thickness t=300nm / / Table 3. The calculated values of inter-planar distance (d-values), with lattice parameter, crystal size for the prepared CIT thin film at (200, 400) C thickness t=600nm / / / According to Optical transmission spectrum of CIT thin films, represent the most accurate method for determining the energy band gap, refractive index n, absorption index k, the absorption coefficient α of semiconductor is based on investigating from the spectral distribution of transmission. To investigate the effect of the annealing temperature on the energy gap of CIT thin films from the transmission T and reflection R at normal incidence in the spectral rang nm with thickness ( ) nm at annealing temperatures (200, 400) C. The optical energy gap were measured optical absorption coefficient α for CIT thin films were calculated by using the Tauc relation in the equation (2): shown in figure 4. It was observed that the values of T are due to the existence of binary phases, this data is in a good agreement with result deduced from XRD that s means increase T increase grain size of crystallites within crease annealing temperature. Α (hʋ)=a/hʋ (hʋ-eg) 1/2 (2) were α is the absorption coefficients A is constant and n=½ refer to indicting a direct energy gap [11]. The transmission curves before and after annealing as

4 4 Falah I. Mustafa et al.: Effect Thickness and Temperature Annealing on Structural and Optical Proportion of CuInTe 2 Thin Film Table 4. Explain Eg value of CIT with thickness (300, 600) nm at different temperature. t (nm) T=R. T T=200 C T=400 C ev 1.15ev 1.18ev ev 1.16ev 1.36ev Fig. 4. Explain T value with wavelength of CIT with thickness (300, 600) nm at different temperature. Refractive index n and the absorption index k for these thin film were calculated from transmission and reflection measurement as shown in the figure 6, it is clear that parameters of n and k at given wavelengths decrease with increasing annealing temperature this change due to the change in the lattice parameter [13, 14] which may be the reason of increase in values energy gap by increasing the annealing temperature. While figure 7. explain ε 1, ε 2 values of CIT with thickness (300, 600) nm at different temperatures. The plot of (αh ʋ) 2 against photon energy of thin film as shown in the figure 5 and table 4 that observed values of the optical energy gap (Eg) are increase with increase in g annealing temperature for both thickness and this change may be attributed to slight changes in the lattice constant this is in agreement with result published by other authors [7]. The refractive index n and the absorption Index k for these thin films were calculated from transmission and reflection measurement as shown in figure 6. Fig. 5. Explain Eg value of CIT thin film with thickness (300, 600) nm at different temperature.

5 AASCIT Journal of Materials 2016; 2(1): Fig. 6. Explainn and k values of CIT with thickness (300, 600) nm at different temperatures. Fig. 7. Explain values ε 1, ε 2 of CIT with thickness (300, 600) nm at different temperature. 4. Conclusion Thin films of CIT as-deposited are amorphous in structure while after annealing temperatures are polycrystalline. The grain size of the particles increases as results of increasing the annealing temperature. It can also be concluded that CIT is a direct band gap semiconductor, that s Eg value increase with increasing annealing temperature as well as thickness. References [1] E. Yassitepe, W. N. Shafarman, I. Shah, Journal of Solid State Chemistry, V. 213 (2014) [2] SM. Wu, YZXue, LM. Zhou, X. Liuand DY. XuDY J. Alloys Compd. V. 600 (2014) PP [3] HR. Hsu, SC. Hsuand YS Liu, Solar Energy, V86 (2012) PP [4] J. L. Orts, R. Dıaz, P. Herrasti, F. Rueda and E. Fats, Solar. Energy Materials & Solar Cells, V. 91 (2007) [5] S. Roy, B. Bhattacharya. SN. Kundu, S. Chaudhuriand AK. Pal. Mater. Chem. Phys. V. 77 (2002.) 365. [6] N. Chahboun, K. ElAssali, A. Khiara, EL Amezianeand T. Bekkay Solar Energy Mater. Solar Cells V. 32 (1994) [7] A. M. Aboelsoud, T. A. Hendia, L. I. Soliman, H. A. Zayed, M. A. Kenawy, J. Material Science. V. 28 (1993) PP. ( ). [8] T. Mise, T. Nakada, Thin Solid Films V518 (2010) P [9] P. Prabukanthan, R. Dhanasekaran, Mater. Res. Bull. V. 43 (2008) PP [10] Manorama Lakhe, Nandu B., Solar Energy Materials & Solar Cells V. 123 (2014) PP [11] L. L. Kasmerski, M. S. Ayyagari, G. A. Sanborn, F. R. White and A. G. Merrill, Thin Solid FilmsV. 37 (1976) PP [12] M. Boustani, K. E1 Assali, T. Bekkay, A. Khiara Solar Energy Materials and Solar Cells V. 45 (1997) PP [13] G. E. A. Muftah. A. P. Samantilleke. P. D. Warren. S. N. Heavens I. M. Dharmadasa J. Mater Sci: Mater Electron V. 21 (2010) V. 21, PP [14] Abhaiman, Shivkumar, Thin Solid Films V 161 (1988) P101.